Power Delivery System Including Interchangeable Cells

ABSTRACT

A power cell system includes a structure that provides multiple power cell locations. The system also includes at least one regenerative power cell, and at least one non-regenerative power cell. The cell locations and power cells are sized and positioned so that each cell location may interchangeably accept either a regenerative power cell or a non-regenerative power cell.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/511,713 filed Aug. 29, 2006 and claims the benefit and priority ofthat application, which is incorporated herein by reference in itsentirety. application Ser. No. 11/511,713 claims priority to thefollowing applications: (i) pending U.S. Provisional Patent ApplicationNo. 60/713,198, entitled “A system and method for a configurable powerinfrastructure including interchangeable cells,” filed Aug. 31, 2005,which is incorporated herein by reference in its entirety; and (ii)pending U.S. Provisional Patent Application No. 60/713,197, entitled“Packaging method for modular multilevel power cells and systeminfrastructure,” filed Aug. 31, 2005, which is incorporated herein byreference in its entirety.

C.-E. NOT APPLICABLE Background

In recent years, circuits for medium-voltage variable frequency drive(VFD) applications have received attention. Several novel methods havebeen introduced in the past decade. For example, in a circuit comprisingseries-connected inverters as described in U.S. Pat. No. 5,625,545 toHammond, the disclosure of which is incorporated herein by reference inits entirety, an inverter or power cell 110 includes a three-phasediode-bridge rectifier 112, one or more direct current (DC) capacitors114, and an H-bridge inverter 116. The rectifier 112 converts the input118 alternating current (AC) voltage to a substantially constant DCvoltage that is supported by the capacitors 114 that are connectedacross the rectifier 112 output. The output stage of the inverter 110includes an H-bridge inverter 116 that includes two poles, a left poleand a right pole, each with two devices. The inverter 110 transforms theDC voltage across the DC capacitors 114 to an AC output 120 usingpulse-width modulation (PWM) of the semiconductor devices in theH-bridge inverter 116.

A circuit including power cells such as 110 in FIG. 1, when connected toa load, such as a motor, can provide power from an input source to themotor when operating in the motoring mode. Such a power cell maysometimes be referred to as a unidirectional or two-quadrant (2Q) cell.This is because when the four quadrants of speed and torque areconsidered, referring to FIG. 2, the operating characteristics 210 ofthis cell are such that it operates in either the quadrant where bothspeed and torque are positive (first quadrant 201) or the quadrant whereboth speed and torque are negative (third quadrant 203).

However, when the motor speed needs to be reduced, power from the motorneeds to be absorbed by the inverter. This mode of operation, when powermust be absorbed by the inverter, is referred to as the regenerationmode. In such situations, regenerative or four-quadrant cells arerequired. An example of a regenerative cell is shown in U.S. Pat. No.6,301,130 to Hammond. As shown in FIG. 3, a regenerative power cell 360may include an active front end 362 that serves as a first converterthat uses insulated gate bipolar transistors (IGBTs) Q5-Q10 or otherswitching devices controlled by PWM. The first converter 362 iselectrically connected in parallel to a second converter 364 and to oneor more DC link capacitors 366. Such a cell receives power from atransformer 346 and delivers it to other cells in the group and a load349. Referring to FIG. 2, this cell permits operating characteristics220 in all four quadrants 201-204, including the quadrant where bothspeed and torque are positive (first quadrant 201), the quadrant wheretorque is positive and speed is negative (second quadrant 202), thequadrant where both speed and torque are negative (third quadrant 203),and the quadrant where torque is negative and speed is positive (fourthquadrant 204).

In the prior art, motor systems included two-quadrant or four-quadrantcells. However, systems that are designed to accommodate one or theother are limited in applicability. The disclosure contained hereindescribes attempts to solve one or more of the problems described above.

SUMMARY

In an embodiment, a power cell system includes a support structurehaving a plurality of cell locations, at least one regenerative powercell, and at least one non-regenerative power cell. The cell locationsand power cells are sized and positioned so that each cell location mayinterchangeably accept either a regenerative power cell or anon-regenerative power cell. Optionally, each cell location may includesupport rails, a power delivery bus positioned to electrically connectwith an input bus of a power cell that is in the cell location, and apower output bus positioned to electrically connect with an input bus ofthe power cell that is in the cell location. In addition, each powercell may include a chassis, such that each chassis in the system hassubstantially the same size and shape as the other chassis in thesystem. The system also may include a wire tray that holds control wirefor each power cell.

In an alternate embodiment, a power cell system includes a plurality ofsupport rails and a back plane that are connected to provide a pluralityof cell locations. The system also includes at least one regenerativepower cell, and at least one non-regenerative power cell. The celllocations and power cells are sized and positioned so that each celllocation may interchangeably accept either a regenerative power cell ora non-regenerative power cell. Each power cell includes a chassis, andeach chassis in the system has substantially the same size and shape asthe chassis for a at least some of the other power cells in the system.Optionally, each cell location may include a plurality of support rails,a power delivery bus positioned to electrically connect with an inputbus of a power cell that is in the cell location, and a power output buspositioned to electrically connect with an input bus of the power cellthat is in the cell location. The system also may include a wire traythat holds control wire for each power cell.

In an alternate embodiment, a power delivery system includes a supportstructure comprising a plurality of cell locations, at least oneregenerative power cell, and at least one non-regenerative power cell.The cell locations and power cells may be sized and positioned so thateach cell location may interchangeably accept either a regenerativepower cell or a non-regenerative power cell. Each power cell may includea chassis, and each chassis in the system may have substantially thesame size and shape as the chassis for a at least some of the otherpower cells in the system. Each cell location may include a plurality ofsupport rails, a power delivery bus positioned to electrically connectwith an input bus of a power cell that is in the cell location, and apower output bus positioned to electrically connect with an input bus ofthe power cell that is in the cell location.

In each of the embodiments described above, each regenerative power cellmay optionally include an inverter bridge, a capacitor set electricallyconnected across terminals of the inverter bridge, and an active frontend that includes a plurality of transistors electrically connected as athree-phase bridge. Alternatively, each regenerative power cell mayinclude an inverter bridge, a capacitor set electrically connectedacross terminals of the inverter bridge, a three-phase diode bridgerectifier electrically connected across the terminals, and aseries-connected transistor and resistor combination that iselectrically connected across the terminals. Also optionally, eachnon-regenerative power cell may include an inverter bridge, a capacitorset electrically connected across terminals of the inverter bridge, anda three-phase bridge rectifier electrically connected across theterminals. Other configurations of regenerative and non-regenerativecells are possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing exemplary characteristics of a priorart non-regenerative power cell.

FIG. 2 depicts operating in four quadrants of speed and torque.

FIG. 3 is a circuit diagram showing exemplary characteristics of a priorart regenerative power cell.

FIG. 4 depicts a circuit comprising a plurality of power cells connectedto a load.

FIG. 5 illustrates an exemplary power cell housing structure.

FIG. 6 illustrates an exemplary support structure for multiple powercells.

FIG. 6 illustrates the support structure of FIG. 6 with a cellpositioned in a cell location.

DETAILED DESCRIPTION

Before the present methods, systems and materials are described, it isto be understood that this disclosure is not limited to the particularmethodologies, systems and materials described, as these may vary. It isalso to be understood that the terminology used in the description isfor the purpose of describing the particular versions or embodimentsonly, and is not intended to limit the scope. For example, as usedherein and in the appended claims, the singular forms “a,” “an,” and“the” include plural references unless the context clearly dictatesotherwise. Unless defined otherwise, all technical and scientific termsused herein have the same meanings as commonly understood by one ofordinary skill in the art. In addition, the following terms are intendedto have the following definitions herein:

-   -   comprising—including but not limited to.    -   electrically connected or electrically coupled—connected in a        manner adapted to transfer electrical energy.    -   H-bridge inverter—a circuit for controlled power flow between AC        and DC circuits having four transistors and four diodes.        Referring to FIG. 1, an H-bridge inverter 116 generally includes        a first phase leg and a second phase leg electrically connected        in parallel. Each leg includes two transistor/diode        combinations. In each combination, the diode is electrically        coupled across the base and emitter of the transistor.    -   inverter—a device that converts DC power to AC power or AC power        to DC power.    -   medium voltage—a rated voltage greater than 690 volts (V) and        less than 69 kilovolts (kV). In some embodiments, medium voltage        may be a voltage between about 1000 V and about 69 kV.    -   non-regenerative power cell—a power cell that does not have the        capability of absorbing regenerative power.    -   power cell—an electrical device that has a three-phase        alternating current input and a single-phase alternating current        output.    -   rank—an arrangement of power cells established across each phase        of a three-phase power delivery system.    -   regenerative power cell—a power cell that has the capability of        absorbing regenerative power.    -   substantially—to a great extent or degree.

In various embodiments, a multi-level power circuit includes a pluralityof power cells to drive a load. FIG. 4 illustrates an exemplaryembodiment of a circuit having such power cells. In FIG. 4, atransformer 410 delivers three-phase, medium-voltage power to a load 430such as a three-phase induction motor via an array of single-phaseinverters (also referred to as power cells). The transformer 410includes primary windings 412 that excite a number of secondary windings414-425. Although primary winding 412 is illustrated as having a starconfiguration, a mesh configuration is also possible. Further, althoughsecondary windings 414-425 are illustrated as having a meshconfiguration, star-configured secondary windings are possible, or acombination of star and mesh windings may be used. Further, the numberof secondary windings illustrated in FIG. 4 is merely exemplary, andother numbers of secondary windings are possible. The circuit may beused for medium voltage applications or, in some embodiments, otherapplications.

Any number of ranks of power cells are connected between the transformer410 and the load 430. A “rank” is considered to be a three-phase set, ora group of power cells established across each of the three phases ofthe power delivery system. Referring to FIG. 4, rank 450 includes powercells 451-453, rank 460 includes power cells 461-463, rank 470 includespower cells 471-273, and rank 480 includes power cells 481-483. Fewerthan four ranks, or more than four ranks, are possible. A centralcontrol system 495 sends command signals to local controls in each cellover fiber optics or another wired or wireless communications medium490.

FIG. 5 illustrates an exemplary power cell structure 510. The power cell510 includes a chassis 512 and a set of power input/output connectors521-525. Exemplary internal components of the cell may include anynumber of capacitors, a heat sink, and an electronics assembly that mayinclude items such as insulated gate bipolar transistor (IGBT) modulesand one or more rectifier modules. The IGBTs may be separated for I/Obus locations and to increase thermal performance.

The chassis 512 encloses various components of the power cell 510, suchas one or more capacitors, printed circuit boards, heat sinks, etc. Thechassis 512 may be fabricated from any suitable material, such asgalvanized steel or another metal, that both mechanically andelectromagnetically isolates the power cell from other power cells inthe system during both normal operation and many abnormal operatingconditions. The chassis 512 may serve to protect internal components ofthe power cell 510 from damage during shipping and handling, and it maybe configured in a manner such that the electronic module 510 can beplaced on any of its sides without causing any damage to the componentsof the electronic module 510. According to various embodiments, thechassis 512 may be comprised of several portions connected together, andone or more portions of the chassis 512 may be removable. In addition,the chassis 512 may be of a thickness sufficient to prevent any debrisresulting from a failure of the internal components of the electronicmodule 510 from exiting the space enclosed by the chassis 512, therebypreventing any collateral damage to other components in the vicinity ofthe electronic module 510.

As shown in FIG. 5, the power cell 510 may further comprise a pluralityof power plug connectors 521-525 coupled to an internal input or outputpower bus that is configured to route power to and from the electronicmodule 510. For example, three of the power plug connectors 522-524 maybe configured to receive three-phase power from a source, while two ofthe power plug connectors 521 and 525 may be configured to deliversingle-phase power to a load. The power plug connectors permit the cellsto be plugged into a master power plane.

The power cell arrangement described in FIGS. 4 and 5 provides amodular, multilevel system that allows cells to be replaced as needed toaccommodate different design requirements, or to replace a failed cell.In addition, the cells 510 shown in FIG. 5 are physicallyinterchangeable so that they may contain either the elements of atwo-quadrant cell, such as the elements shown in FIG. 1, or the elementsof a regenerative (four-quadrant) cell, such as the elements shown inFIG. 3. In this manner, individual cell locations can be populatedreplaced as with regenerative or non-regenerative cell as necessary toprovide for a desired degree of braking. The chassis 512 of each cell510 will thus have substantially the same size and shape, regardless orwhether it is a regenerative cell or non-regenerative cell.

FIG. 6 illustrates an exemplary support structure 644 for multiple powercells, such as nine cells, within a housing wherein each power cell orother electronic module is positioned on one or more mounting rails 646so that the rear of each cell faces a backplane 648 and the cell's powerplugs contact the cell power connections 621-625 through the backplane648. The backplane 648 may be fabricated from any suitablenon-conductive material, such as a high-strength non-conductive laminatematerial, and it provides a barrier between individual cells and otheraspects of the system.

The support structure is designed to provide a plurality of celllocations 650, each of which may receive an interchangeable cell (suchas 510 in FIG. 5) that is either a regenerative cell or anon-regenerative cell. In this manner, a single power cell system mayinclude all regenerative cells, all non-regenerative cells, or somemixture of regenerative and non-regenerative cells depending on thedesired degree of braking. A cell 510 may be sized to slide into a celllocation 650 along the support rails 646, and the cell's power plugswill then engage the cell power connections 621-625. Optionally,additional connections such as wire trays 630 may be provided toaccommodate control wires that are routed to and from the cells. Alsooptionally, one or more secondary power busses 628 may be provided forthe direction of current to or from each cell. FIG. 7 illustrates theexemplary support structure 644 with a power cell 510 positioned in oneof the cell locations.

Still other embodiments will become readily apparent to those skilled inthis art from reading the above-recited detailed description anddrawings of certain exemplary embodiments. It should be understood thatnumerous variations, modifications, and additional embodiments arepossible, and accordingly, all such variations, modifications, andembodiments are to be regarded as being within the spirit and scope ofthis application

1. A power cell system, comprising: a support structure comprising aplurality of cell locations; at least one regenerative power cellconfigured to function as a regenerative power cell; and at least onenon-regenerative power cell configured to function as a non-regenerativepower cell; wherein the cell locations and power cells are sized andpositioned so that each cell location may interchangeably accept eithera regenerative power cell or a non-regenerative power cell such thatboth the regenerative power cell and the non-regenerative power cell arefunctioning concurrently.
 2. The system of claim 1, wherein each celllocation comprises: a plurality of support rails; a power delivery buspositioned to electrically connect with an input bus of a power cellthat is in the cell location; and a power output bus positioned toelectrically connect with an input bus of the power cell that is in thecell location.
 3. The system of claim 1, each regenerative power cellcomprises: an inverter bridge; a capacitor set electrically connectedacross terminals of the inverter bridge; and an active front endcomprising a plurality of transistors electrically connected as athree-phase bridge.
 4. The circuit of claim 1, wherein each regenerativepower cell comprises: an inverter bridge; a capacitor set electricallyconnected across terminals of the inverter bridge; a three-phase diodebridge rectifier electrically connected across the terminals; and aseries-connected transistor and resistor combination that iselectrically connected across the terminals.
 5. The system of claim 1,wherein each non-regenerative power cell comprises: an inverter bridge;a capacitor set electrically connected across terminals of the inverterbridge; and a three-phase bridge rectifier electrically connected acrossthe terminals.
 6. The system of claim 1, wherein each power cellcomprises a chassis, and each chassis in the system has substantiallythe same size and shape as the other chassis in the system.
 7. Thesystem of claim 1, further comprising a wire tray that holds controlwire for each power cell.
 8. A power cell system, comprising: aplurality of support rails and a back plane that are connected toprovide a plurality of cell locations; at least one regenerative powercell configured to function as a regenerative power cell; and at leastone non-regenerative power cell configured to function as anon-regenerative power cell; wherein the cell locations and power cellsare sized and positioned so that each cell location may interchangeablyaccept either a regenerative power cell or a non-regenerative power cellsuch that both the regenerative power cell and the non-regenerativepower cell are functioning concurrently; and wherein each power cellcomprises a chassis, and each chassis in the system has substantiallythe same size and shape as the chassis for a plurality of other powercells in the system.
 9. The system of claim 8, wherein each celllocation comprises: a plurality of support rails; a power delivery buspositioned to electrically connect with an input bus of a power cellthat is in the cell location; and a power output bus positioned toelectrically connect with an input bus of the power cell that is in thecell location.
 10. The system of claim 8, each regenerative power cellcomprises: an inverter bridge; a capacitor set electrically connectedacross terminals of the inverter bridge; and an active front endcomprising a plurality of transistors electrically connected as athree-phase bridge.
 11. The circuit of claim 8, wherein eachregenerative power cell comprises: an inverter bridge; a capacitor setelectrically connected across terminals of the inverter bridge; athree-phase diode bridge rectifier electrically connected across theterminals; and a series-connected transistor and resistor combinationthat is electrically connected across the terminals.
 12. The system ofclaim 8, wherein each non-regenerative power cell comprises: an inverterbridge; a capacitor set electrically connected across terminals of theinverter bridge; and a three-phase bridge rectifier electricallyconnected across the terminals.
 13. The system of claim 8, furthercomprising a wire tray that holds control wire for each power cell. 14.A power delivery system, comprising: a support structure comprising aplurality of cell locations; at least one regenerative power cellconfigured to function as a regenerative power cell; and at least onenon-regenerative power cell configured to function as a non-regenerativepower cell; wherein the cell locations and power cells are sized andpositioned so that each cell location may interchangeably accept eithera regenerative power cell or a non-regenerative power cell such thatboth the regenerative power cell and the non-regenerative power cell arefunctioning concurrently; wherein each power cell comprises a chassis,and each chassis in the system has substantially the same size and shapeas the chassis for a plurality of other power cells in the system; andwherein each cell location comprises a plurality of support rails, apower delivery bus positioned to electrically connect with an input busof a power cell that is in the cell location, and a power output buspositioned to electrically connect with an input bus of the power cellthat is in the cell location
 15. The system of claim 14, eachregenerative power cell comprises: an inverter bridge; a capacitor setelectrically connected across terminals of the inverter bridge; and anactive front end comprising a plurality of transistors electricallyconnected as a three-phase bridge.
 16. The circuit of claim 14, whereineach regenerative power cell comprises: an inverter bridge; a capacitorset electrically connected across terminals of the inverter bridge; athree-phase diode bridge rectifier electrically connected across theterminals; and a series-connected transistor and resistor combinationthat is electrically connected across the terminals.
 17. The system ofclaim 14, wherein each non-regenerative power cell comprises: aninverter bridge; a capacitor set electrically connected across terminalsof the inverter bridge; and a three-phase bridge rectifier electricallyconnected across the terminals.
 18. The system of claim 14, furthercomprising a wire tray that holds control wire for each power cell.